X-Band MMIC Active Mixers

In this paper two active MMIC mixers for RF front-end applications are described. A down-converter that converts an RF signal(fRF=10.45 GHz)into an IF signal(fIF=0.95 GHz)using an LO signal(fLO=9.5 GHz)and an up-converter that performs the opposite process have been fabricated. The down-converter is designed using the topology of a dual-gate pHEMT, while the up-converter is implemented in the form of a double balanced mixer using the topology of the Gilbert cell and the occupied areas are approximately0.78 mm2and3.86 mm2, respectively. Both mixers present conversion gain, very low input and output return losses, very good isolation between all of their ports and the required LO power is quite low, while the up-converter contains on chip, except for the dc-bias and matching sub-circuits, the required LO and RF baluns. Both circuits have been fabricated using the H-40 process of GEC-Marconi. Section 1 presents fundamentals on mixer theory and mixer design while in Section 2 the characteristics of H-40 process are described. In Section 3 and in Section 4 the designing, the simulated and the measured results of the down-converter and the up-converter are presented, respectively.